DE4203345A1 - High performance emitter, esp. for UV light - comprises discharge chamber filled with gas, and metallic outer electrodes coated with UV-transparent layer - Google Patents

Abstract

High performance emitter, esp. for UV light, comprises a discharge chamber (4) filled with a gas that emits radiation under discharge conditions. The wall of the chamber (4) is partially formed by a 1st dielectric(1) having, on its surface facing away from the chamber, metallic lattice or network outer electrodes(5) coated with a UV-transparent protective layer(8a) or embedded in such a layer. The emitter has a 2nd electrode(3) bordering the chamber(4) and this electrode has a 2nd electric(2) next to the chamber(4). An alternating current source(6) is connected to the 1st (5) and 2nd (3) electrodes to inject discharge. The novelty is that the protective layer(8a) contains inorganic oxides, pref. oxides of Si. ADVANTAGE - The outer electrode protects against corrosion and erosion.

Description

Technical area

The invention relates to a high-power radiator, especially for ultraviolet light, with a discharge space filled with a filling gas under discharge conditions radiation emits, the wall of Entla at least partially by a first dielectric is formed, which on its off the discharge space th surface with metallic grid or net-shaped outer electrodes is provided, which outer electrodes with a UV-transparent protective layer are coated and / or in egg ner are embedded, and with a second electrode, which either itself adjoins the discharge space or a having second dielectric, the at the discharge space borders, and with one to the first and second electrodes closed AC power source for feeding the discharge.

The invention makes reference to a prior art, as he is from the older European application 9 11 08 604.9 dated 27 May 1991 of the Applicant.

Technological background and state of the art

The industrial use of photochemical processes depends strongly from the availability of suitable UV sources. The klas UV lamps produce low to medium UV intensities at some discrete wavelengths, such as. B. the Mercury low-pressure lamps at 185 nm and in particular at  254 nm. Really high UV powers are only obtained High-pressure lamps (Xe, Hg), but then their radiation over distribute a larger wavelength range. The new Excimer lasers have some new wavelengths for basic photochemical experiments are provided currently for cost reasons for an industrial process well only suitable in exceptional cases.

In the aforementioned EP patent application or in the Conference Print "New UV and VUV Excimer Heaters" by U. Kogelschatz and B. Eliasson, distributed at the 10th Vortragsta Association of German Chemists, Section Photoche mie, in Würzburg (FRG) 18.-20. November 1987, will be a new one Excimer radiator described. This new radiator type is based on the basis that excimer radiation is also quenched can generate electrical discharges, a discharge type, which is used industrially in ozone production. In the short-term (<1 microsecond) existing Stromfila Menten this discharge are by electron impact Edelgasa excited to excited molecular complexes (excimers) react further. These excimers live only a few 100 nanoseconds customers and give their binding energy in the form of decay UV radiation off.

The structure of such Excimerstrahlers corresponds to towards the power supply largely that of a classic ozone generator, with the essential difference that at least one of the discharge space limiting electrodes and / or Dielectric layers permeable to the generated radiation is. These electrodes must in addition to the high UV transmission u. a. still have the following properties: good conductivity Electricity, low cost, good flexibility Creating as intimate contact with the Dielek trikum and long life. The long life requires in particular a low chemical reactivity with the Umge exercise of the spotlight. If you want to use the spotlight as the light source use chemical reactors, so is for many applications  even chemical inertness to some substances unbe necessary.

Another unwanted reaction is the sometimes violent Corrosion and erosion of the outer electrodes and thus verur gentle pollution of the radiator, this way one much of the UV power loses because of the dirt layer is almost impermeable to UV light.

In order to eliminate the shortcomings described, is in the one cited in the cited patent application, at least the External electrodes to be provided with a protective layer or she to embed in such. As a coating or insert In particular, dielectric materials are suitable here substances that make good contact with the dielectric of the radiator produce and at the same time are easy to apply. Become while still using materials that are UV-curing can harden them extremely fast by the spotlight itself. Charak teristic for the subject matter of the earlier application is the Use of organic embedding materials.

Brief description of the invention

Based on the known, the invention is the task The external electrode is reliable against corrosion and corrosion To protect erosion.

This object is achieved in that the Protective layer as an essential ingredient inorganic oxides, in particular oxides of silicon.

Preferably comes as a protective layer material water glass, Both sodium and potassium water glass in question. Such protective layers are of interest here Wel lenlängenbereich (100 to 600 nm) transparent, the Transparency at wavelengths below 200 nm decreases.  

The protective layer prevents corrosion and erosion on the outer electrodes. In addition, the generation of Sliding discharges along the periphery of the radiator largely suppressed because the protective layer also acts as insulation.

Particular embodiments of the invention and thus achieved Other advantages are described below explained in more detail on the drawings.

Brief description of the drawings

In the drawing, embodiments of high performance radiators in a simplified form; shows

Fig. 1 shows a UV cylinder radiator of known design;

Figure 2 shows a detail of the outer dielectric tube of a UV lamp with arranged thereon outer electrode coated with water glass round wire.

Figure 3 shows a detail of the outer dielectric tube of a UV lamp with arranged thereon outer electrode of round wire, wherein the entire outer surface is provided with a coating material of water glass.

Figure 4 is a detail of the outer dielectric tube of a UV lamp having disposed thereon outer electrode made of round wire, which is located in recesses of the outer dielectric tube, which are in turn filled with a coating of water glass.

Figure 5 is a detail of the outer dielectric tube of a UV lamp having disposed thereon outer electrode made of round wire with a smooth outer dielectric tube and a Dickschichtvergußmasse of water glass, in which the electrodes are embedded.

Fig. 6 shows a detail of a UV emitter, which emits radiation both outward and inward.

Detailed description of the invention

The UV high-power radiator shown schematically in Fig. 1 consists of an outer dielectric tube 1 , z. B. quartz glass, a concentric inner Diel arranged elektrikumsrohr 2 , the inner wall is provided with an inner electrode 3 . The annular space between the two tubes 1 and 2 forms the discharge space 4 of the radiator. The inner tube 2 is gas-tightly inserted into the outer tube 1 , which was previously filled with a gas or gas mixture, which emits UV or VUV radiation under the influence of silent electrical discharges.

As the outer electrode 5 is a metal mesh or Metallgit ter, which extends over the entire circumference of the outer tube 1 . Both the outer electrode 5 and the outer dielectric tube 1 are permeable to the UV radiation produced.

The electrodes 3 and 5 are 6 to the two poles of an AC power source. The AC source basically corresponds to those used to feed ozone generators. Typically, it provides an adjustable AC voltage in the order of several 100 volts to 20,000 volts at frequencies in the field of technical alternating current up to several 1000 kHz - depending on the electric dengeometrie, pressure in the discharge space 4 and composition of the filling gas.

The filling gas is, for. As mercury, noble gas, noble gas metal vapor mixture, inert gas-halogen mixture, optionally under Use of an additional additional noble gas, preferably Ar, He, Ne, as a buffer gas.

Depending on the desired spectral composition of the radiation can thereby a substance / substance mixture according to the following Use the table:

filling gas radiation Helium | 60-100 nm neon 80-90 nm argon 107-165 nm Argon + fluorine 180-200 nm Argon + chlorine 165-190 nm Argon + krypton + chlorine 165-190, 200-240 nm xenon 160-190 nm nitrogen 337-415 nm krypton 124, 140-160 nm Krypton + fluorine 240-255 nm Krypton + chlorine 200-240 nm mercury 185, 254, 320-370, 390-420 nm selenium 196, 204, 206 nm deuterium 150-250 nm Xenon + fluorine 340-360 nm, 400-550 nm Xenon + chlorine 300-320 nm

In addition, a whole series of other filling gases come into question:

• A noble gas (Ar, He, Kr, Ne, Xe) or Hg with a gas or vapor of F ₂ , J ₂ , Br ₂ , Cl ₂ or a compound which in the discharge contains one or more atoms F, J, Split off Br or Cl;
• a noble gas (Ar, He, Kr, Ne, Xe) or Hg with O₂ or ei a compound which in discharge has one or more ozone Atoms split off;  
• - a noble gas (Ar, He, Kr, Ne, Xe) with Hg.

In the forming silent electric discharge (silent discharge), the electron energy distribution by thickness the dielectrics and their properties pressure and / or temperature be optimally adjusted in the discharge space.

When an AC voltage is applied between the electrodes 3 , 5 , a multiplicity of discharge channels (partial discharges) are formed in the discharge space 4 . These interact with the atoms / molecules of the filling gas, which ultimately leads to UV or VUV radiation.

In the detail of FIG. 2, the individual wires 7 of the outer electrode hen with a coating 8 of water glass verse. This can be made in the simplest case by who the that the wire was dipped in water glass prior to its further processing. As is known, the highly alkaline water glass applied rapidly polymerises under atmospheric or acidic conditions to form polysilicic acids, thereby forming the known properties.

In the detail of FIG. 3 is not only the wire, but the entire radiator surface with a coating 8 a of What serglas provided. Although this arrangement reduces the UV lamp output for very small wavelengths, it can be produced particularly easily by immersing the fully assembled spotlight in a bath of water glass, or by spraying or painting on a glass of water and then hardening it. At a 308 nm radiation and a typical layer thickness of 1 to 2 microns, the Trans mission is more than 90%.

In the arrangement shown in Fig. 4, the individual wires 7 of the outer electrode 5 lie in recesses of the outer dielectric tube 1 and are completely embedded in the coating 8 b of water glass. The layer 8 b then has alternately different thickness along the radiator surface. Since thin layers better durchlas sen the generated UV radiation than thick, there is a corresponding Intensitätsmu art. This is advantageous for applications in which an object to be UV-irradiated is moved along the surface and well-defined exposure pauses should occur.

In Fig. 5, finally, the arrangement of completely in egg ner water glass mass 8 c embedded wires on a smooth outer dielectric tube 1 is illustrated.

In addition to cylindrical radiators, the invention Ver settlement of the electrodes can also be applied to surface radiators with success. Also, the outer electrode itself may be designed differently, z. B. not mesh or lattice-shaped, but only consist of parallel strips, which lends itself in particular in an arrangement according to FIG. 3.

Also, instead of separate or discrete Elektrodenanord calculations such that are applied by strip or git ternetzförmige metallizations on the outer surface of the Di elektricumsrohres 1 and then provided with the described in connexion with Fig. 3 way with a protective layer.

The invention has been explained above with reference to Ausführungsbeispie len, which refer to so-called outdoor radiator hen. The presented measures to protect the Elek electrodes of course also apply to a so-called internal radiator. Apart from the position of the transparent elec trodes 5 , such an inner radiator corresponds to the outer radiator shown in Fig. 1.

Furthermore, radiator configurations are possible in which the UV radiation is emitted both to the outside and to in NEN. Fig. 6 illustrates a section of such a radiator. In such arrangements, both dielectric tubes 1 , 2 and also the respective electrodes 3 , 5 must be transparent to the generated radiation. In the case, both the first electrode 5 and the second electrode 3 can then optimally protected in the manner outlined above from chemical and physical attacks who the.

Outdoor and indoor heaters are regularly cooled with a liquid coolant. In the case of external radiators, this is conducted through the inner dielectric tube 2 ; in the case of inner radiators, the coolant surrounds the outer dielectric tube 1 . Again, protective layers of water glass contribute to preventing or at least reducing the erosion attack by the coolant.

Claims (6)

1. high-power radiator, in particular for ultraviolet light, with a discharge space ( 4 ) which is filled with a filling gas which emits radiation under discharge conditions, wherein the wall of the discharge space ( 4 ) at least partially by a first dielectric ( 1 ) is formed, which On its the discharge space ( 4 ) facing away from the surface with metallic grid or net-shaped outer electrodes ( 5 ) is provided, which outer electrodes ( 5 ) with a UV-transparent protective layer ( 8 , 8 a ...) are coated and / or in such and a second electrode ( 3 ) either directly adjoining the discharge space ( 4 ) or having a second dielectric ( 2 ) adjoining the discharge space ( 4 ) and having one of the first ( 5 ) and second electrode ( 3 ) connected to the AC power source ( 6 ) for feeding the discharge, characterized in that the protective layer ( 8 ; 8 a; 8 b, 8 c) as the essential Bestan Part of inorganic oxides, preferably oxides of silicon. 2. High-power radiator according to claim 1, characterized in that the protective layer ( 8, .. ) consists essentially of water glass or other inorganic oxides. 3. High-power radiator according to claim 1 or 2, characterized in that only the material from which the outer electrode ( 5,3 ) is made, with the protective layer ( 8 ) is provided ( Fig. 2). 4. High-power radiator according to claim 1 or 2, characterized in that at least the outer electrode ( 5 ) and at least the surface of the first dielectric ( 1 ) in the region of the outer electrode with the UV-transparent protective layer ( 8 a) are provided ( Fig ). 5. High-power radiator according to claim 1, 2 or 4, characterized in that the outer surface of the first Dielek tricum ( 1 ) and / or the inner surface of the second Dielek tricum ( 2 ) is provided with regular depressions, in which the electrodes ( 5 , 3 ) is at least partially embedded and the wells with a water glass mass ( 8 b) are filled, which completely covers the electrodes ( 5 , 3 ). 6. High-power radiator according to claim 1, 2 or 4, characterized in that at least the outer electrode ( 5 ) in a protective layer ( 8 c) is embedded from a UV-transparent mass.